Large-scale sediment wave structures were discovered on the Conrad Rise, Indian sector of the Southern Ocean. The sediment waves are most likely formed by bottom current interactions with the Antarctic Circumpolar Current (ACC). Based on the seismic survey, it is thought that the ACC was migrated to the north at about 1.5 Ma.Winter sea-ice edge was significantly shifted to the north at least about 15 degrees as latitude during the last glacial period. This indicated that the Southern Ocean surface water was stratified due to input of less saline water. In addition, the millennial-scale cooling and sea-ice expansion were occurred in the glacial South Indian Ocean.